Parahistricostoma tuberculatum (C. L. Koch & Berendt, 1854 ) Mitov & Perkovsky & Dunlop, 2021

Mitov, Plamen G., Perkovsky, Evgeny E. & Dunlop, Jason A., 2021, Harvestmen (Arachnida: Opiliones) in Eocene Rovno amber (Ukraine), Zootaxa 4984 (1), pp. 43-72 : 61-63

Parahistricostoma tuberculatum (C. L. Koch & Berendt, 1854) comb. n.

Figs 22–24

Nemastoma tuberculatum C. L. Koch & Berendt 1854: 97–98 , pl. 11: fig. 97. For a full description of the holotype see Dunlop (2006: 176, 179, fig. 5B).

Histricostoma (?) tuberculatum: Staręga 2002: pp. 602–603 . Dunlop 2006: p. 179; Dunlop & Mitov 2009: 351–355 , figs 1–2, 6–8; Elsaka et al. 2019: 156.

Synonymy. See Dunlop (2006: 179)

Holotype. MB.A. 1612; ex Berendt collection, repository number 7248. Baltic amber; Palaeogene (Eocene); precise locality unclear.

Distribution. Baltic and Bitterfeld amber ( Staręga 2002; Dunlop 2006; Dunlop & Mitov 2009; Elsaka et al. 2019).

Diagnosis: As for the genus.

Material examined. UKRAINE: SIZK K-25396, SIZK K-7460. Rovno region, Sarny District, Klesov, Pugach quarry; late Eocene; ( Figs 22–24 ). Syninclusions: SIZK K-25396, decaying plant remnants; insect larva; SIZK K- 7460, two Acari (one Oribatida ).

Description. SIZK K-25396 is a male specimen, body and legs covered by a white emulsion dorsally; the prosoma and part of the opisthosoma obscured by an air-pocket. The fossil is clearly visible only ventrally ( Fig. 22 ). Body and limbs (in amber) black. L: 1.25, abdomen width: 0.88. The armament of the scutum and the dorsal granulation/microsculpture of the body as well as the ocular tubercle are not visible. Only the tips of three of the four pairs of dorsal spines are visible. Chelicerae: basal segment equivocal, length of distal segment: 0.43, movable digit length: 0.17; basal article distally with apophysis; the cheliceral apophyses are shaped like an ‘ice cream scoop’ ( Fig. 23 ), directed slightly downwards and resemble boxing gloves in dorso-lateral outline; see also Dunlop & Mitov (2009). The length/height of the apophyses is 0.126. The cheliceral apophyses and the frontal distal segment of the chelicerae bear strong setae. One of the setae, located distally at the apex of the apophysis, is twice as long (ca. 0.04 mm) as the others. The opening of the cheliceral glands/secretion area is probably located on the medial depressions of the apophysis ( Fig. 23 : white arrow). Cheliceral basal segment laterally spinulate; Palps with article lengths of: Tr: 0.25, Fe: 0.84, Pa: 0.77, Ti: 0.53, Ta: 0.29; as Ta:Ti = 0.55. Pedipalps elongate and slender, without apophyses (spurs/thorns/denticles).

Palpal trochanters more cylindrical than oval. Palpal coxa and trochanter ventrally covered with denticles ( Fig. 23 ). Distal end of the patella slightly curved downwards. Palpal tibia slender, baseball bat-shaped – basally dilated; palpal tarsus slender, club-shaped in dorsal/ventral view, laterally machete-shaped – distally rounded and slightly dilated. Palpal articles (except trochanters) ventral with clavate setae (L: 0.042).

Legs long and slender. Femur length (pseudoarticulations of leg femora in parentheses): Fe I: 1.33 (with three pseudoarticulations, middle); second pair of legs missing; Fe III: 1.44 (with 3 pseudoarticulations, central); Fe IV: 1.33 (with 5 pseudoarticulations, centro-basal). Trochanters of the legs with spinule-like microsculptural elements ( Fig. 23 : black arrow), similar to those in Histricostoma creticum and H. drenskii . Microsculpture elements of the leg femurs include loose-textured denticles and granules. Metatarsal and tarsal leg segments densely setose. Legs with 10–16 tarsal segments, ending with a single claw.

Description. K-7460 is a male specimen, ventrally covered by a white emulsion ( Fig. 24 ), dorsally not well visible due to fractures in the amber and due to an air-pocket adjacent to the legs and body. Four pairs of slender, pillar-like spines, each slightly bulbous at the top, can be seen. The dorsal granulation/microsculpture of the body is not visible. Body and limb color (in amber) black. Body length: 1.3–1.4, abdomen width: 0.80. Ocular tubercle: length: 0.15 and width: 0.25; diameter of each lens: 0.06; Chelicerae: basal article distally with apophysis. Pedipalps elongate and slender, without apophyses. Palpal trochanter more cylindrical than oval. Palpal tibia slender, baseball bat-shaped – basally dilated; palpal tarsus slender, baseball bat-shaped in ventral view ( Fig. 24 ). Palps with article lengths of: Ti: 0.69–0.73, Ta: 0.38; Ta:Ti = 0.52–0.55; the remaining palpal segments cannot be measured correctly. The distal end of the patella curves slightly downwards. Palpal segments (except trochanters) with clavate setae (L: 0.042) ventrad. Legs long and slender. Segments of Leg I with lengths of: Fe: 1.58, Pa: 0.32, Ti: 0.85; Leg III with article lengths of: Fe: 1.71, Pa: 0.32, Ti: 0.80; tarsus ends in a single claw. The pseudoarticulations and the microsculpture of the leg femora are obscured. The leg trochanters are spinulate – their microsculpture is similar to that in Histricostoma creticum and H. drenskii .

Remarks. For additional morphological data see Dunlop & Mitov (2009: 351–355, figs 1–2, 6–8).

Figures

FIGURES 22–24. Parahistricostoma tuberculatum (C. L. Koch & Berendt, 1854), males, from Rovno amber (Klesov, Pugach quarry, Ukraine), late Eocene. 22 SIZK K-25396, detail of the body and limbs, ventro-lateral view. 23 SIZK K-25396, detail of 22, closer view showing the chelicerae with characteristic ‘ice-cream scoop’ shaped apophyses (ap) and its secretion area (white arrow), and also the basal segments of the legs and pedipalps; note the spinule-like microsculptural elements of the leg trochanters (Tr, black arrow). 24 SIZK K-7460, detail of body and limbs in ventral view, showing basally dilated palpal tibia (Ti) and baseball bat-shaped palpal tarsus (Ta). Scale bars: 22, 24: 1 mm; 23: 0.5 mm.